Regionalization of trauma services continues to be a national priority, reflecting its potential for reducing mortality and morbidity from injuries. The regional systems that have been developed across the country include transport, triage and specialty centers for severe trauma, burns, and head and spinal cord injuries. With the introduction of per case payment, and particularly the Medicare DRG methodology, issues of the sensitivity of DRGs to severity have been raised, and limitations acknowledged. Although this concern is raised for many categories of disease, it is particularly important for regional trauma systems since severity is the basis of triage, with high cost facilities maintained to respond to serious injury. The recognition of the importance of measuring severity reliably has been long recognized in the trauma field and widely applied measures such as the Abbreviated Injury Score (AIS) have been developed. The objective of this research is to test three methods for trauma casemix classification: (1) DRGs, (2) DRG's modified by AIS and (3) and AIS based classification system to be developed. Contrasts to Disease Staging will be made to assess relative homogeneity of each method for explaining variations in length of stay, charges and intensity of care. Financial implications of per case payment under three methods (Medicare, New Jersey and state wide average), using the alternative casemix measures will be estimated for hospitals in Maryland, a highly regionalized system. This will provide a basis for assessing the strength of incentives that could hinder or reverse regionalization efforts. The research also will identify which approaches to casemix-severity measurement are most appropriate, and propose approaches for intergrating severity measurement into DRGs.